It is common practice to use aqueous polyurethane-urea dispersions as a film forming resin in cosmetic and dermatological compositions as exemplified by recent patents in haircare (U.S. Pat. Nos. 5,626,840; 5,968,494; 6,007,793; 6,106,808; 6,106,809; and 6,113,881), skincare and makeup (U.S. Pat. Nos. 5,643,581; 5,962,620; and 5,972,354), and nailcare (U.S. Pat. Nos. 5,965,111; 6,080,413; and 6,106,813).
It is generally recognized that higher molecular weight polyurethane-urea polymers provide certain performance benefits to cosmetic formulations when compared to lower molecular weight polyurethane-urea polymers. It is generally believed that higher molecular weight materials have enhanced durability, abrasion resistance, and humidity resistance.
U.S. Pat. No. 6,106,808 (Bhatt et al.) discloses a hair spray composition comprising (1) about 0.25% to 6% of a carboxylated polyurethane resin having a weight average molecular weight of about 10,000 to 25,000, (2) 0% to about 6% of a second hair fixative resin; (3) 0% to about 80% of an alcohol; and (4) about 15% to 99% water. All percentages are by weight. It is stated that the carboxylated polyurethane resin provides an elastic, flexible film on hair giving it a natural feel. The second hair fixative resin functions to reduce flaking attributed to the carboxylated polyurethane resin and to impart stiffness to the hair spray composition.
U.S. Pat. No. 6,007,793 (Bhatt et al.) discloses another hair spray composition comprising (1) about 0.25% to 6% of a carboxylated polyurethane resin having a weight average molecular weight of about 15,000 to 150,000; (2) 0% to about 80% of an alcohol; and (3) about 15% to 95% water. All percentages are by weight. This patent, unlike U.S. Pat. No. 6,106,808, does not rely on optional second hair fixative resin and uses higher molecular weight carboxylated polyurethane resin.
Higher molecular weight polymer, however, generally translates to a higher viscosity, thus bringing with it possible difficulties in preparing aqueous polyurethane-urea dispersions. To reduce the viscosity, organic solvents can be used while preparing the aqueous dispersion. The solvents may need to be removed, adding steps and complexity to the formulation preparation. In a high viscosity formulation, it may be difficult to achieve dispersions with a small particle size. Such an effect tends to cause difficulty in forming smooth coalesced films in use, thereby reducing gloss and durability, among other properties. Some skilled in the art have used organic coalescing agents, possibly to ensure good film formation. See, e.g., U.S. Pat. No. 6,080,413 (Ellingson et al.) at column 6, starting at line 42. In cosmetic applications, the higher viscosity caused by high molecular weight polymers may lead to a draggy or greasy feel in use and during dry down.
Efforts have been made to provide the benefits and at the same time to minimize the drawbacks of using high molecular weight aqueous polyurethane-urea dispersions in cosmetic formulations. U.S. Pat. No. 5,637,292 (Thomas) delivers an aqueous dispersion of low molecular weight acrylated urethane oligomer and photoinitiator to the nail. The dispersion is dried, then cured using ultra-violet light to achieve a high molecular weight coating. The invention may require the use of an ultra-violet light source.
U.S. Pat. No. 5,681,550 (Rubino) adds 1 to 10% of hardening agents, such as epoxy resins or urethane polymers, to crosslink with the polyurethane-urea dispersion to achieve high molecular weight.
U.S. Pat. No. 5,965,111 (Ellingson et al.) discloses a fast-drying nail polish composition comprising (1) a film-forming, water-borne polymer; and (2) a liquid diluent. Various water-borne polymers are disclosed, including polyurethanes, polyacryls, and styrene-acryl copolymers. The film-forming polymers may be crosslinked to provide properties such as chip resistance and superior hardness. The patent discloses using multivalent metallic cations, such as Zn+2, to ionically crosslink negatively charged moieties, such as sulfonates and carboxylates, either in the composition itself or after application and film formation.
A need exists for an aqueous polyurethane-urea dispersion which can be easily prepared and readily formulated into cosmetic and dermatological compositions for skin, nails, and hair to provide improved abrasion resistance, transfer resistance, and humidity resistance while providing excellent gloss, feel, and adhesion.